CAM201 Lecture Notes - Lecture 1: Thrombin Time, Direct Thrombin Inhibitor, Prothrombin Time
30 Jun 2018
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Coagulation Tutorial 1
Case 1 65 year old female with a history of atrial fibrillation.
1) What are the possible causes of these coagulation abnormalities?
Medication for atrial fibrillation- NOACs, warfarin
Warfarin prolongs PT (and so INR) more than APTT- especially due to
supratherapeutic amounts of warfarin
History suggests warfarin
NOACs- dabigatran affects APTT more than PT, but not useful for
monitoring the drug as the APTT plateaus after a certain dose of the drug
Unfractionated heparin (UFH)- generic heparin- inhbits Factors II, IX, and
X- also prolongs APTT
Unfractionated heparin (UFH)- generic heparin- inhbits Factors II, IX, and
X- also prolongs APTT. It may increase PT in very high doses
Therefore, more likely to be warfarin given history and PT
It could also be rivaroxaban
Liver disease- affects both, but more PT
Vitamin K deficiency
DIC- less likely, but possible- normal platelet count, but usually less
fibrinogen
Factor deficiency- in the common pathway- single or multiple
2) What other information would you want to find out to appropriately manage
this patient?
History- medication
Liver disease risk factor- especially if they’re not on blood thinners
Vitamin K deficiency- dietary or malabsorption- treat it to test
a) Routine blood ordered, patient well- ask about diet, if she has any bleeding,
withhold warfarin and retest, modify warfarin dose if needed, check for dosing
error, other drug interactions
b) Perioperative assessment for hip arthroplasty- give Vitamin K or reschedule surgery
c) Acute subdural haematoma- stop warfarin, give Vitamin K, give her some clotting
factors- prothrombin complex concentrate (prothrombin X) or donated plasma
Case 2 45 year old male. History of jaundice and fatigue.
Thrombocytopenia
Low fibrinogen count
High APTT and PT
1) What are the possible causes of these coagulation abnormalities?
Liver disease- liver produces most of the factors and plasma proteins
Low platelet count- due to reduced thrombopoeitin function, portal
hypertension which causes splenomegaly, trapping platelets.
DIC- disseminated intravascular coagulation- due to malignancy
(adenocarcinoma), sepsis, trauma (particularly head), obstetric
complications (placental abruption)
2(a) Which cause do you think is the most likely here?
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Document Summary
Warfarin prolongs pt (and so inr) more than aptt- especially due to supratherapeutic amounts of warfarin. Noacs- dabigatran affects aptt more than pt, but not useful for monitoring the drug as the aptt plateaus after a certain dose of the drug. Unfractionated heparin (ufh)- generic heparin- inhbits factors ii, ix, and. It may increase pt in very high doses. Therefore, more likely to be warfarin given history and pt. Liver disease- affects both, but more pt. Dic- less likely, but possible- normal platelet count, but usually less fibrinogen. Liver disease risk factor- especially if they"re not on blood thinners. Liver disease- liver produces most of the factors and plasma proteins. Low platelet count- due to reduced thrombopoeitin function, portal hypertension which causes splenomegaly, trapping platelets. Dic- disseminated intravascular coagulation- due to malignancy (adenocarcinoma), sepsis, trauma (particularly head), obstetric complications (placental abruption) Increased destruction, decreased production, or sequestration of platelets.
